Various storage devices for dental products are known from the prior art. Filler materials are often packed in small cartridges. However, there are also filler materials which, before their use, have to be prepared by mixing two pasty substances. These substances are usually applied from tubes or screw tubes and are mixed on a mixing block. This requires uniform dosing and a large number of maneuvers.
DE 90 00 839 U discloses a package for multi-component adhesive in small quantities, the components of the adhesive being arranged in bowl-shaped chambers between two interconnected films. By tipping one of the bowls over, its content can be transferred into the other bowl.
EP 0 916 593 A2 describes a flexible package for separate storage and simultaneous dispensing of two materials of a polymerizable system, in particular of an addition-crosslinking dental impression material, into beaker-shaped depressions.
EP 0 115 562 A1 describes a portioning package for storing and mixing silver and mercury, comprising two portioning packages which are made integral by a pair of films welded to one another to form two separate portioning pockets.
A multi-component chamber bag for storing liquid substances is described in DE 199 27572 A1, for example.
None of said devices permits both the storage of substances and also substantially loss-free mixing of these substances into a pasty material using the storage device.
Consequently, it is an object of the present invention to provide a device making it possible to store and mix substances, especially pasty substances.
This object is achieved by a device and by a method for producing the device, as described below.
The terms “comprise” and “contain” within the meaning of the invention introduce a nonexhaustive list of features. Likewise, the word “one” is to be understood in the sense of “at least one”.
The invention has the following advantages:
In the device according to the invention, the substances to be mixed can be packaged optimally in the required quantity. Incorrect dosing and incorrect mixing ratios are largely ruled out.
After the cover film and bottom film have been pulled off, the substances to be mixed are present in the state ready for mixing and do not first have to be pressed out of different vessels or transferred to a container for mixing. The storage area is part of the mixing area. In this way, 100% of the pre-dosed quantities which are to be mixed are available for mixing. The mixed paste can thus be used substantially without residues.
The base film serves at the same time as a mixing surface after the cover film has been pulled off and its material properties can be adapted to the reactivity of the substances which are to be mixed.
The term “chamber” is to be understood as a hollow space which is closed off from the outside and which is formed by connection of at least two films (base film or bottom film and cover film or top film), for example by adhesive bonding, sealing, heat-sealing or high-frequency sealing, and can be peeled completely open by pulling the films off or apart in the sealing area.
The chambers can be arranged in any desired way, but preferably in such a way that mixing is readily possible after activation of the device. The chambers are arranged substantially centrally, if appropriate along one axis on the nonactivated device.
The volume of the at least two chambers can be enlarged if appropriate by slight thermoforming, in particular of the cover films, in this area. The chamber volume to be chosen is dependent on the intended use and in principle unlimited. Suitable chamber volumes are usually in the range of 0.01 through 10 ml.
The term “not substantially thermoformed” or “only slightly thermoformed” within the meaning of the invention means that the ratio of diameter to depth of the chamber is greater than or equal to 5:1, preferably greater than or equal to or flatter than 10:1.
The chambers can have any desired shape, but they are preferably round or oval. In the case of two-component and multi-component materials, oval chambers arranged one behind the other may be practical for reasons of space, in which case the small ellipse radii are preferably arranged substantially along the longitudinal axis of the device.
Droplet-shaped chambers are also expedient, in which case the “droplet tip” points to the optionally provided ribbing of the film or to an optionally provided tab.
In this way, the device is easier to open because the force to be applied initially to pull off or peel off the film in the area of the droplet-shaped tip of the sealed seam is slight and increases only gradually to the force needed to pull off the film in the area of the full width of the sealed seam.
This effect can also be achieved if the sealing area surrounding the chambers has a shape with at least one area which narrows in one direction and which points in the direction of an optionally provided pull-off tab.
In order to ensure that the chambers are fully opened in a manner which is substantially uniform and free from residues in order to form a plane mixing area, it has proven expedient for the chamber, or the sealing area surrounding it, to be designed gradually tapering to a point also on the side of the chambers remote from the tab.
If the device has a plurality of chambers, it has proven expedient if the sealing areas forming the chamber are connected to one another, in order to ensure uniform opening of the chambers upon activation of the device. An hourglass-shaped connection area is preferred.
Such a design of the sealing edge connection between two chambers largely ensures that the substances to be stored and to be mixed are not spilled upon activation of the device.
When the chambers are arranged transversely with respect to the longitudinal axis of the device, it has proven expedient if each chamber or its sealing area has a droplet tip pointing in the direction of an optionally provided ribbing. The droplet tips of the sealed seams can in this case also open into a common tip.
“Activation” within the meaning of the invention is to be understood as opening the device by pulling the cover film or top film off or up from the base film or bottom film, exposing a substantially plane mixing area on which the substance or substances to be mixed are located.
If appropriate, the device has a pocket in which an applicator suitable for mixing and application is situated.
The term “pocket” is to be understood here as a container open at least on one side. The shaping of the pocket can be effected by one sealed seam, individual sealed webs and/or sealed points.
To prevent contamination of the mixing area during storage (mixing area=area needed for mixing the material portions), it may be expedient to run a narrow peelable seam around this area. This seal is completely opened upon activation of the device and if appropriate likewise has a sealed seam tip pointing to the pull-off tabs or ribbings in order to make it easier to detach the films sealed to one another.
The applicator preferably has the shape of a spatula and can be made of wood, metal or a suitable plastic. If appropriate, the applicator has an angled shape or, depending on the width, a nonrectangular or round, beveled end. An angle in the range of 5 to 45° relative to the longitudinal axis is preferred.
The use of an angled applicator permits mixing on the device according to the invention and handling in the manner to which, for example, a dentist's assistant is accustomed when using a mixing block. In contrast to the device according to the invention, a mixing block has a certain height relative to, for example, a table surface acting as its support and it thus also permits mixing using a straight spatula.
It can also be advantageous if base film and cover film are componnet parts of a single film, which can also be a multi-layer film. In this embodiment, the flat mixing surface is formed by pulling apart the base film or bottom film and the cover film or top film, without the cover film or top film being completely pulled off or removed.
The term “flat mixing area” within the meaning of the invention is to be understood as an area which, during mixing with an applicator, does not throw up any folds and has substantially no depressions or only very slight depressions which are negligible in terms of the intended use.
Surprisingly, it has been found that in certain aluminum composite films, depending on the film structure, a thermoforming ratio of between 5:1 and 10:1 is possible, and in which, during the mixing process on the mixing area with the aid of a suitable applicator, the thermoformed areas can be restored again by upsetting to a fold-free film.
However, the fact that a substantially flat mixing area is formed upon activation of the device does not rule out the possibility of mixing the substances on a conventional mixing block after they have been scraped off onto the latter.
Depending on the application, the mixing area has a surface in the range of 5 to 300 cm2.
The device preferably has holding arrangements in the edge area, which holding arrangements are intended to make it easier to handle the device during mixing.
Such holding arrangements can be in the form of ribbings in the edge area of the device and can be introduced into the film, for example by embossing.
However, it is also possible to provide two ring-shaped tabs or to punch holes or slits, in particular two slits in the longitudinal direction, in the edge area of the device, which make it easy to hold the activated device. This permits mixing of the substances on the mixing area even without a solid support.
It can also be advantageous to apply adhesive areas as a profiled coating or as two-sided adhesive points or adhesive strips which make it easier to fix the activated device to a surface. These adhesive areas can, if appropriate, be on a turned-back film of the device or can be covered with additional cover film to prevent premature adhesion.
Depending on the area of use, it may be sufficient if the device has individual adhesive areas only in the edge areas. It is also conceivable, however, that the films of the device are made almost completely adhesive on the side directed away from the substance. In this embodiment, the device, for mixing purposes, could be positioned almost stationary on a surface.
Alternatively, the device can also be arranged on a block with an adhesive surface. Each side of the block can be used for several mixing applications until, after contamination or wear, a fresh adhesive sheet is used. The individual sheets or component parts of the block are in this case preferably not coated completely with an adhesive, but instead have an area which is free of adhesive and allows the individual sheets or component parts to be pulled off.
It can also be useful to use an adhesive block which has a partial adhesive coating in a surface area set in by 1 to 5 mm (i.e. smaller) than the activated device to be fixed thereon. This makes it easier, for example, to position the device on the adhesive block in the desired manner.
The arrangement of only one adhesive area in the edge area of the device and the alternate adhesion of several devices permits an advantageous packaging in the form of a dispenser. After one device has been removed from the dispenser, a new device is made ready for removal from an opening in said dispenser.
Adhesives which are particularly suitable are, inter alia, encapsulated adhesives (nanoparticles) which exert their adhesive property only when pressed onto a surface, for example. The adhesives are preferably of such a nature that they can again be removed from a surface without leaving any residue, for example from a table or mixing block serving as mixing support. A mixing plate with clamping ridges at both ends can also be used to clamp the pull-off tabs during the mixing process.
The device has at least one chamber, but can also have two, three, four or more chambers if appropriate, into which substances to be mixed can be introduced.
The provision of one chamber may be sufficient, for example, if the stored material tends to segregate during storage and has to be mixed again before use.
The device can preferably be produced in a simple and cost-effective way by “folding over” or “folding together” a single film and sealing it at least in the edge area of the chambers which are to be formed and into which the substance to be stored is introduced before sealing.
Planar side-sealed bags are conventionally sealed only on three sides, then filled via the unsealed opening, and this remaining opening is finally sealed. During the filling process, the as yet unsealed area is often contaminated with the filler material. This area has to be cleaned in order to guarantee the tightness of the fourth sealed seam.
According to the invention, it has been found that planar devices for storing and/or mixing of substances can also be produced and filled in a simpler manner.
The method for producing the device according to the invention comprises the following steps:    a) providing a base film or bottom film,    b) if appropriate, partial thermoforming of the film so that the ratio of diameter to depth of the thermoformed area is greater than or equal to 5:1, preferably greater than or equal to 10:1,    c) applying at least one substance onto the film which, depending on the film material used for the cover film or top film and on its deformation by thermoforming, has a sufficiently high stability to ensure that it cannot escape laterally during the sealing operation,    d) sealing a cover film or top film on, preferably directly after step c), without the base film or bottom film from step a) having been thermoformed, and the base film or bottom film and the cover film or top film can be constituents of one film.
The sealed seam generated in step d) is closed upon itself. It is, for example, round, oval, rectangular, diamond-shaped or droplet-shaped.
Another method for producing the device comprises the following steps:    a) providing a base film or bottom film,    b) turning the film back preferably to form a fold area,    c) forming at least one sealed seam which intersects the fold area, at least two pocket-shaped arrangements being formed,    d) introducing at least two substances separately into the corners of the pocket-shaped arrangements,    e) sealing the pocket-shaped arrangements.
If appropriate, before step d), the pocket-shaped arrangements in the fold area can be widened by applying pressure parallel to the main direction of the sealed seam. This facilitates introduction of the substances and prevents the as yet unsealed areas from being contaminated with substances to be introduced.
To produce a device which is suitable for storing three components to be mixed, the following method has proven expedient:    a) providing a base film or bottom film,    b) applying a first substance on a site of the subsequent fold area,    c) turning the film back preferably to form a fold area,    d) forming two intersecting sealed seams which also intersect the fold area, with one chamber and two pocket-shaped arrangements being formed,    e) introducing at least two substances separately into the corners of the pocket-shaped arrangements,    f) sealing the pocket-shaped arrangements.
In all of the methods, the sealed seams can have any desired shape.
If the substance to be stored is flowable, it should preferably have a viscosity in the range of 0.5×10−3 to 10×103 Pas.
Upon production and filling of the device, the speed at which the chambers are sealed must be adapted to the viscosity or stability of the substances which are to be sealed-in.
A sufficiently high speed also makes it possible to seal relatively fluid substances between a substantially flat top film and bottom film, since, depending on its surface tension and its viscosity, the substance, after it has been applied to the bottom film, requires a certain time to disperse thereon or requires a certain time to spread into the area formed by the sealing of the top film or cover film on the bottom film, and to flow into the actual sealing area. This area should therefore be sealed promptly.
In one of these embodiments, a film is first made ready onto which a certain quantity of substance or substances to be mixed is applied, the film is folded preferably centrally and is sealed together in a peelable manner to leave at least one chamber in which the substance or substances are located, and the at least one chamber can also be located in the fold area.
The chambers are formed by sealing or adhesively bonding at least one or two films at least in the edge area of the chamber to be formed, leaving free a hollow space in which the substance to be mixed is located.
Depending on the embodiment, one or more of the sealing areas which form the chamber can also be replaced by a crease or fold which arises when the film is bent. In this case, the sealed seam is not closed on itself, but instead forms with the fold at least one closed chamber.
The sealing can be done in a manner familiar to the person skilled in the art, for example by heat-sealing or by ultrasonic sealing.
It can also be advantageous if the film areas which are pulled apart for opening the device do not correspond to the fold areas with which the device can be fixed, in particular clamped, after activation.
For this purpose, a film is preferably chosen which when folded forms no or only very slight kinks or the film in the fold area is turned back in such a way that when the cover film is pulled off or the cover film and base-film are pulled apart, no depressions are left in the fold area which could impair the mixing result. It is also conceivable not to fold the film via a sharp edge, but only to turn it back loosely so that a bead-shaped configuration remains in the fold area.
Films which are particularly suitable are those films, including multiple-layer films, which, when pulled off, do not permanently deform and/or warp, and in particular do not show a tendency to roll up, so that the formation of a substantially plane mixing surface is guaranteed.
If the film used has a tendency to roll up, it can be advantageous for the latter to be laid, during production, offset by 90° relative to the longitudinal axis of the device in order, after activation of the device, to prevent or reduce the rolling inclination of the film causing a restoring effect about the fold area of the film upon production of the device.
Peelable films are normally used which, when pulled off, can be separated from one another at the seal areas.
Foil materials which have proven advantageous are, for example, PE, PP, PA, PET, PVDC, PVC, EVA, EVOH, COC and paper/plastic composite films or a PE/paper composite. A combination with a paper/aluminum/paper/PE film sequence is preferred.
The films preferably have barrier layers in the form of vapor-deposited metal, such as aluminum, or ceramic, such as SiOx or AlOx.
For storing substances which are particularly sensitive to light, the use of aluminum composite films or opaque printed films has proven expedient. However, colored transparent films are also suitable.
The device according to the invention and the method according to the invention are suitable for storing and mixing any substances, said substances usually being present in a pasty consistency after they have been mixed.
In the case of substances which tend to polymerize under exclusion of oxygen, it is recommended to use single-layer films or laminated films without an oxygen-tight barrier layer such as aluminum. For storing what are called resin-modified glass ionomer cements, however, these films should form the most efficient possible water vapor barrier. Single-layer films such as sealable PE or PP films in an appropriate thickness of between 80 and 1000 μm or plastic laminate films with additional plastic barrier layers such as PET, EVOH, EVA, PA, COC, PVC, PVDC or thin aluminum or ceramic deposits (Al2O3, SiOx) are conceivable. Thick single-layer films of greater than 200 μm can also be injection-molded and, in the case of a one-piece embodiment, can be made thinner at the kink point.
The substances which can be stored in the device and can be mixed with the aid of the device can be present as powder, granulate, in tablet form, as paste or as liquids.
The substances are, in particular, constituents of dental filler materials, such as composites, compomers, glass ionomer cements, or veneering materials, fixing cements, or crown and bridge materials. However, depending on the embodiment, impression compounds based on polyether or silicone can also be stored with the aid of the device.
The device is also suitable, however, for storing and mixing multi-component adhesives such as epoxide resin adhesives, or multi-component coloring agents. A hue mixed individually from two different colors can also be prepared by at least partial mixing of two color portions.
In order to guarantee sufficient storage stability and straightforward mixing, the substances and the outer layer of the base film should be adapted to one another so that the substances remain on the base film when the cover film is pulled off and they are not at least partially pulled off along with the cover film.
This can be achieved by using suitable coating materials, either by anti-adhesion coating of the cover film, for example with silicone oil or silicone varnish or erucamide varnish or PTFE in this area, if appropriate as a profiled coating and/or application of an adhesion promoter or application or incorporation of a micro-retentive surface on the base film. It is also conceivable for the substances which are to be stored to be coated with a suitable coating agent. Further suitable separating agents can be separating wax or sealing wax, which has an anti-adhesion effect in the unsealed area.
Similar effects can be achieved by applying a nano coating, as is described for example in VDI Nachrichten 1/01, page 9.
To avoid capillary effects, which can lead to the substances stored in the device “creeping” into sealed areas, it can be advantageous if the sealing area forming the chamber(s) is interrupted by a narrow unsealed area. In this area, the base film is preferably separated from the cover film by a groove-like hollow surrounding the chamber, which hollow is formed as a thermoformed profile in the cover film.
Depending on the field of application, however, it may also be expedient if, after activation of the device, the substance adheres both to the base film and also to the cover film. When the device is activated by means of the cover film or top film being pulled apart or off the base film or bottom film, then, depending on how the substance to be mixed is arranged on the base film, it is in this way divided, on the exposed mixing area, into two separate mixable portions.
This embodiment has proven particularly useful when using filler materials in dentistry, if the quantity of substance stored in the device is sufficient for more than one cavity.
Since, in this field, the substance normally begins to polymerize only after the mixing or begins to set, for example by a cement reaction, this embodiment makes it possible for only one portion of the stored quantity of substance to be mixed and processed initially, while the second portion remains unmixed on the mixing area.
By applying an anti-adhesion coating to either the cover film or base film, it is possible to ensure that, after activation of the device, the substances to be mixed remain adhering to only one of the films. In this way, it is possible to ensure that, in a device with two chambers, only two paste fields are formed after activation, and the mixing distance can be kept short.
After activation, i.e. after the cover film or top film has been pulled up or off, the device ready for mixing preferably has an elongate shape, for example the shape of an ellipse or a rectangle.
Different embodiments of the device according to the invention are described below.